With the popularity of baking and roasting, aluminium foil is often used to wrap food for baking and roasting at home. However, what is aluminium foil made of? Is it more appropriate to have the shiny side or the dull side of aluminium foil to be in contact with food? Is it truly safe to wrap food in aluminium foil?
What is aluminium foil made of?
The aluminium foil that we usually refer to was originally made of tin in the past (tinfoil). However, the low melting point of tin (231℃) made it not suitable for roasting under high temperatures. In addition, tinfoil is not good for packing food due to its stiffness. Aluminium, with a melting point of 660℃ and a boiling point of 2467℃, is comparatively less likely to be melted into food during roasting. Being one of the most abundant metals on earth, aluminium features high malleability, tensile strength and corrosion resistance. Therefore, it replaced tin as the major ingredient for making kitchen foil, and the aluminium foil products available on the market now are all made of aluminium.
Why can aluminium foil be used to wrap food for cooking?
Featuring high thermal conductivity and a high boiling point, aluminium foil is used to wrap food, especially meat, to prevent it from direct exposure to flames that might burn the food and generate toxic chemicals such as acrylamide. In addition, aluminium foil can also prevent the loss of moisture and preserve tenderness in food after cooking.
Is it really harmless for direct contact of aluminium foil with food?
It is often reported that an excessive amount of aluminium accumulated in the human body damages human brain cells and results in memory loss. However, people should not be overly worried as the melting point of aluminium is 660℃, making it unlikely to melt when the food is being grilled. As long as aluminium foil that fulfils quality requirements is used, it is very unlikely that aluminium will move to food. As a result, there is no need to completely stop using aluminium foil in cooking. Even if aluminium is consumed through food, under normal consumption circumstances, it will not be absorbed by the human body and the majority of aluminium consumed by human will eventually be excreted through the digestive tract. According to the current information of the World Health Organization (WHO), there is no evidence indicating that aluminium leads to development of Alzheimer’s disease. 
How to use aluminium foil properly?
First of all, aluminium foil produced by qualified manufacturers that meet the safety standards must be chosen. In addition, acidic substances may separate aluminium from the foil, and it is therefore advised to avoid cooking acidic food, such as lemon, vinegar or tomato sauce, wrapped in aluminium foil.
As its name suggests, aluminium foil is metal in essence and therefore cannot be used in the microwave. On the one hand, it prevents food from being heated up as microwaves cannot penetrate metals. On the other hand, metal reflects microwaves and damages the microwave tubes, creating electric sparks, and even causing fire and explosion. On the contrary, aluminium foil is safe to use in ovens as they are traditional heating method.
Is it more appropriate to have the shiny side or the dull side to be in contact with food?
The appearance of a shiny side and a dull side of aluminium foil is simply a result of the milling process. To prevent the aluminium foil from breaking, two layers of foil are milled together for production. During the process of mutual contact, the side that is in contact with another layer becomes dull, while the other side in contact with the machine becomes shiny. In fact, it makes no big difference in the time for using the two sides for heating food. Nevertheless, it is advisable to use the dull side for direct contact with food because food may stick to the shiny side more easily.
 Risk Assessment of Dietary Exposure to Aluminium in Chinese Population (China National Food Safety Risk Assessment Committee)
 Is Aluminium Foil Safe for Grilling? (Hong Kong Consumer Council)